Glass drawing tank



Aug. 1, 1933. H. L.. HALBACH GLASS DRAWING TANK Filed June 25. 1952 INVENTOR Patented ug. 1, 1933 l 1,920,692- oLAss DRAWING TANK Howard L. Hamann, Clarksburg', W'. va., assigner to Pittsburgh Plate Glass Companyya Corpo- `ration o Per'msylvania Appiieatitn annees, 1932, serial Nd, 618,830 f sclaims. (01.149417) The invention relates to a, glass drawing ltank from which sheet glass `is to be drawn and relates particularly tothe claywork usedin the glass bath from which' the sheet is drawn.Y Heretofore a cut off gate or` shearcake has been.r

. used at the entrance end of the draw tank or dog house to cut off the heatJ from the melting tank, and a iioating skimbar has been used intermediate the gate `and the point of `draw in `order to' prevent surface impurities from working along 'the surface of the bath and becoming incorporated into the "sheet One object of theipresent improvement is'to combine the cut oli4 gate and skim bar and .thus simplify the` structure. A further and `more important object is to construct the skim bar so that the operation oriskirnming the bath between the i Ui skim bai" and the line of draw is partly, or en` -tirely, eliminated Thisskimming operationhas always been necessary atshort intervals to avoid the formation fof lines in theglass sheet on the `side next to the melting tank. The lines come from the skim bar, andare due' to the reaction of. the glass on the clay of the skirn bar at the surface of the glass. This reactionroughens the surface of the clay so that the glass skin which goes into the surface of the sheet' is roughened CII or lined instead of beine perfectly smooth, as

" `labor and introduces defects into the sheet duel to the disturbance of the bath. Cold glass which is pulled to the sides of th'ebath `by the skimming iron becomes `incorporated into the edges `of the sheet tending to cause unevenness and breakage.` In some cases also bubbles are incorporated into they glass due to the use` of `the iron. f

Briefly stated the requirement forskimrning structing it so that the glass'lying next to the skim bargis caused to circulate `downward into the4 mainbody of glass beneathl As a result, the defects formed in the'surface skin of glass which touchesthe skim bar are `not incorporated into the surface of. theslass. sheet. Certain embodibar and are stretched out into threads orstrings,`

is avoided with the improved skim bar by con-- ments of` the invention are- `illustrated iny vthe `accompanying drawing, wherein: g gh v l, lFigure 1 is a vertical section throughthe-ap- And Figs.,2, 3 `and 4 are partial secparatus.

Itions showing modifications.4

AReferringtoi'ig. l, thereference numeral 1 fnvdicatesthe-end` of the melting" tank which may be `of any approved type andlis a.V drawing extension or doghouse which communicatesatits left hand end with the melting tank; `The glass `sheet?l `is drawn continuously from `the body of molten f cut into sectionsin the usual way. A draw bar 12 `of, refractory material lies inthe body of fr glassin' the extension 2 and. performs the usual 4functions of maintaining the position oi the 4line of draw and giving a cooler layer of glass from which to draw the sheet than would be the case if the draw'barr were not employed. The cover Afor the'forehearth rollers 4, 4, .5, 5, etc. which carry'the glassiup` i 'wa'rdly in a continuous ribbon through the leer casing 6 at thetopof which casing the glass is comprises the clay members "7, 8, 9 and -1O ary ranged as Vshown `in the drawing with `the space j 11 between the members 8v andf9 for the passage y of the sheet. i f Located between theentrance of the eXtensionZ and the draw bar lfis a combined skim bar and cut' 05T` gate 13 which isl supportedfinttheyposi-` ltion shown by any suitable means.V This blockhas its upperportion above the `surface of the glass so that it acts as'acut cil preventing the passage point` from which the sheet 3 is drawn. This r,cut off gate permits of more even control of tempera-` ture conditions in the portion `of* the tank from which the sheet is drawnas isV well known in the of the heated gases from the melting tank to the.

art. In order to better protect the portion :of vthe y member `13 lying above the surface of th'e'lglass, 'the front and rear portions are covered with layers 1,4, 14 ofrnaterialwhich is more refractory than the' main body of the bar.v The portionof the'bar which lies below the surface of. the gate has its fronttface 'inclined downwardlyjand fori ingthereab'ove at the point A somewhat from the radiation of heat from the body of glass beneath the bar. As a' result the glass jat this` point is.

cooler than would otherwise be 'the case/and cooler than the glass lying therebeneath. Thiscooler glass, therefore, tends to move downward,

as indicated by the arrow B, and, commingle'iwith the hotter glass flowing vto the right through the extension, as indicated by the arrow'C. 'This downward circulation along the inclined surface 15 thus carries downward any defective glass formed at the surface of the bath where it touches theskim bar. The defects at the surface of the glass under these conditions are kept from moving along the surface of the bath and being drawn up into the surface of rthe sheet 3. Since the defects are eliminated by carrying them downward into the main' body of glass, it becomes unnecessary to skim the bath, so that with a skimming bar constructed as shown, this skimming operation may be eliminated and a sheet produced which is free from lines and free from defects ordinarly incident to or resulting from the skimming operation. The

skim bar is located at a substantial distance from themeniscus (curved base) oftheglasssheetbeing drawn, so that the surface flow of glass toward the.l sheet will not carry with it the cooler surface glass closely adjacent tothe skim bar, which, as here-` tofore explained, must circulate downwardly in order to avoid defects from the bar being carried into the sheet. Thedefinition. of the location of the bar as remote `from the meniscus of the,

sheet,y as used in the claims, is intended to define va separationl of suchdimension as to permitthat part of the suriacezglass lying above the forward extension 15 'on 'the yskim bar to move toward the bar and downwardly. v

' Fig. 2 illustrates a modification in which the lower portion 16 of the skim bar has an inclination less than that in the Fig. 1 constructiomas indicated at l'. The upper portion 18 of the skim bar is also provided with an overhang 19 which is not found the construction .of Fig. 2. This `arrangement* gives the same general result as heretofore explained in connection with Fig. 1'.y

Fig. .3 illustrates a further modification in which the skim bar 20 and gate 2l are made separate instead of being made in one piece as in the construction-of Fig. 1. The gate 2l in this case v isplaced at the entrance of the drawing exten- 'sion which is'the common arrangement `in the y art. The skim bar 2D has substantially the same shape as the lowerportion of the member 13 in the Fig., 1 construction and thefunction accom* plished incident to the inclined surface 22 is the same as that heretofore described in connection` with the Fig. l construction. if -it is desired to secure anadditional cooling effect upon the glass atthe point A, this may be accomplished by providing a groove in the upper portion of the skim bar and tting a pipe 23 in this groove through which a coolingr flow of liquid is passed. much cooling7 however, must be guarded against as excessive cooling is inclined to produce devitriricationD Numerous-other variationsof the construction may be made, the result to be accomplishedin each case being the cooling of the glass4 where its surface contacts with the front face of the skim bar so a downward circulation is produced to break the skin on the surface of the glass, carry any defects at thispoint downward and thus avoid the necessity of frequent applications of a skimming iron as has heretofore been hang 19 of the Fig. 2 construction. circulation of glass along the inclinedl surface is `Figs illustrates a modification in which the skimbar 24 is provided with a shelf 26 lying at` thelower edge oj the inclined'surface 27, and with an overhang. 28 corresponding to the over- A downward Too produced, as explained in vconnection with'the other modications.

What I claim is: f

1,. Inv combination in apparatus for 'making sheet glass` including a melting tank and ra drawing extension communicating therewith, means for drawing a` glass sheet from the extension, and a skimk bar of refractory materiallying in the glass bath between the inlet end of the drawing extension and the line of draw remotefrom the meniscus of the sheet having its side toward the line of ydraw extending downwardly and forwardly from theglass level. v. l

' 2. l'n .combinationv ink apparatus for making sheet'glass includinga melting tank and a `dr'awing extension communicating therewith, means for drawing a glass sheet from the extension, and a skim bar of'refractory4 material lying partly above 'and partly below the-surface of glass between the line of draw of the glass sheet andV tl e melting tank remote from the". meniscus of the and having its front face inclined ior- Y wardly so as to partially shieldy the glass lying above the shelf next to the surface yof the bath from the radiant heat of the body of glass directly beneath the bar. f

3. In combination inI sheet glass includinga melting tank and a drawing. extension communicating therewith, means for drawing aA glass sheet from the extension, and a skim bar of Vrefractory material lyingfpartly above and partly below the surface of glass between the line of draw of the glass sheet and the melting tank. remote' from the i'neniscvusV of the sheet and having its front face in a plane which apparatus for making Y is upright' but inclined away from ther line `of."

draw from its lower edge up. f f

4. In combination in vapparatus for making sheet giass including a melting tank and a draw-l ling extension cornnninicating therewith, having a 5. In combination. in apparatus for` making ,sheet glassincluding a melting tank and a draw ing extension communicating therewith,` means for drawing a glass sheet from the extension, and

a skiinbar offrcfractory material lying in the glass bath between the inlet end of the drawing extension and the line of draw remote from the meniscus of the sheet having its side toward the line of draw provided with a forwardly extending shelf below the surface of the glass.

6. In combination in apparatus for' making sheet glass including a melting tank and a drawing extension communicating-therewith, `means for drawing av glass `sheet from they extension,

and a skim bar of refractory material lying in the glass bath between the inlet end of the drawing extension and the line ofA draw remote from the meniscus of `the sheet having its side toward the line of draw provided withl two forwardlyexytending shelves, one lying belowv the surface of the glass andthe other above such surface.

` HOWARD L.- HALBACH. 

